You have to take the allen bolt out and the magnet holder has an internal thread that you can use to get a grip. I use the same norton tool for removing the rocker shafts from the head, it is a sliding hammer and does the job nicely. You could make one yourself if you can find or make a stud with the right thread, unfortunately i am away travelling at the moment or I would see what thread it is, however I'm sure some of the other forum members will know.
You don't have to use a slide hammer.
The Boyer rotor (magnet) thread should be 5/16" UNF (24tpi) and to remove it screw in a bolt of that size, then tap the bolt head gently up/down/left/right a few times and the rotor should loosen.
Thank L.A.B. it worked like a chame, thank also to dave M.
I didnt realise the seal goes on the inside of the timing cover, still the boyar rotor has to came off to get the timing cover off to replace the seal.
Make sure that you use some protection (no pun intended) when you put the timing cover back on. The cam-shaft end can damage the new seal when you put the cover back on, there is a special tapered tool available to avoid this but actually a bit of masking tape carefully applied round the shaft has the same effect.